1. Field of the Invention
The present invention relates to contactless power supply devices using resonance coupling.
2. Description of the Related Art
Contactless power supply devices for wirelessly supplying power to electronic devices without power cords or the like have been put to practical use. There are various wireless power supply techniques for supplying power to electronic devices that are separated, and an electromagnetic induction method and an electromagnetic wave transmission method are widely used. Further, in recent years, an electromagnetic resonance method, an electric field coupling method, and the like have attracted attention.
In an electromagnetic induction method, power is supplied using electromagnetic induction coupling generated between a power transmission coil and a power reception coil; thus, it is necessary to place the coils very closely.
In a magnetic resonance method, a magnetic field generated by supply of power to a power transmission coil is received in a power reception coil by using resonance coupling, the magnetic field is converted into power, and the converted power is supplied to an electronic device. This method comparatively strongly copes with positional deviation between coils; thus, a power transmission distance can be made long.
In the case where power is supplied from one contactless power supply device to one power supplied device, the resonance frequency of a power transmission coil preferably agrees with the resonance frequency of a power reception coil. Thus, in the case where power is supplied to a plurality of power supplied devices, power can be transmitted with high efficiency with the use of a plurality of power transmission coils having different specific resonance frequencies.
Patent Document 1 discloses a contactless power supply device for selectively supplying power to a plurality of power supplied devices having different specific resonance frequencies by discretely or successively changing the resonance frequency of one power transmission coil.